The long-term goal of this laboratory is to understand the detailed structural mechanisms employed by cytoskeletal proteins in order to produce force and mediate interactions with their various intra- or intermolecular protein targets. For ATP-driven molecular motors, as well as the GTP-driven G-protein family of molecular switches, conformational states are governed by the presence or absence of the nucleotide o-phosphate. An intriguing question is: how proteins can sense such small conformational changes and then amplify them, sometimes by several orders of magnitude, in order to achieve their specific cellular function? This proposal aims to explore structure/function relationships in the dynamin protein family, which consists of large GTPases involved in functions such as endocytosis, vesicle trafficking, maintenance of mitochondrial morphology, and viral resistance. Although there is evidence that dynamin drives membrane fission via a force-generating mechanism, there is much debate as to whether it actively generates force, or rather acts a regulator of endocytosis. Our goal for the five-year project is to answer three major questions: 1) What structural features enable dynamin to form polymeric rings around the necks of endocytotic vesicles? 2) What is the structural basis for regulation of dynamin's GTPase activity? 3) What conformational changes take place in dynamin as it cycles through its GTP hydrolysis cycle? We will investigate these questions by solving the high-resolution X-ray crystal structure of one or more proteins from the dynamin superfamily in different nucleotide states, as well as identifying and structurally characterizing dynamin mutants. [unreadable] [unreadable]